Conventional internal combustion engines (DE AS No. 12 13 670) have manifolds which are designed as castings and which are very heavy as a result of their great wall thickness. Although it is the aim in modern automotive engineering to avoid heavy parts to the greatest possible extent, nothing has changed in the past in the mode of construction of manifolds because no other possibility of controlling the high temperature differences between the cooled cylinder block and the manifold, which is subjected to the considerably higher exhaust gas temperatures, was in sight. For example, the use of individual steel pipes had to be ruled out from the outset because of the high production expenditure.
On a known manifold which is constructed according to the unit-assembly principle (DE OS No. 15 76 357), there is associated with each cylinder outlet an outlet elbow and a short pipe length which are combined so as to form a T-shaped component consisting of two half shells. The adjacent pipe line lengths are interconnected through flanges. A manifold of this kind, which consists of many components, tends to become permeable in its numerous pipe connections when subjected to the action of heat.
The invention has set itself the task of providing a light-weight-construction manifold which is specially adapted to a six-cylinder in-line engine and which permanently withstands the high thermal stresses.
To solve this problem, the invention proposes
that the manifold should consist of two partial manifolds, of which one connects the first three cylinders and the other connects the remaining three cylinders, and PA0 that each partial manifold should be composed of two half shells which form, for each of the three cylinders, connecting sockets flanged thereto as well as a collecting pipe which is common to all the connecting sockets, and PA0 that the half shells should have in the zones bounded by the connecting sockets and the collecting pipe web sheets which areally adjoin the separation plane and are welded together, and PA0 that in each collecting pipe there should end, in the zone of a half shell, a pipe socket with a flanged part for the connection of the exhaust piping.
The chosen half-shell form allows a simple production by stamping or pressing. As a result of the manifold being divided into two partial manifolds, the thermal expansions are kept within limits so that the arising thermal stresses can be absorbed by the manifold. Due to the welded connection in the separation plane, the two half shells of the manifold form a constructional unit that is stable within itself. Any residual thermal expansions are compensated for through the pipe sockets which are each connected to one half shell and are flanged to the exhaust piping.
Decisive for the stability of each manifold unit composed of two half shells is the areal connection of the web sheets by edge welding and spot welding. It is only by this means that the required resistance to warping and distortion is brought about, particularly in the plane of the web sheets.
The stability of the manifold units is additionally improved in that the mouths of the connecting sockets and the pipe sockets are received in corresponding bores in connecting flanges and are welded together with these.
For reasons of output co-ordination, it is expedient that a first partial manifold connects the first three cylinders and the second partial manifold connects the remaining three cylinders. The exhaust gases are then separately conducted through the pipe sockets from the partial manifolds in an exhaust system comprising two pipes.
The sheet construction has the additional advantage that, because of its small mass, it is very rapidly heated up in the cold starting phase, causing the high exhaust-gas temperatures desired for the exhaust has purification to be reached at a particularly early stage.
Expediently, the half shells will be manufactured from heat-resistant steel sheet, preferably of a ferritic structure, which is characterised by a minimal thermal expansion.
Although the most favourable realisation of the invention is given on a six-cylinder in-line engine, it can of course also be applied to an in-line engine having eight cylinders, each partial manifold being connected to four exhaust-gas ports. However, the proposed division into two partial manifolds can be useful even if only four cylinders are provided.